1. Technical Field
The present invention relates to steering systems and suspension systems for motor vehicles, and more particularly to steering systems and suspensions systems for motorized tricycles, or trikes.
2. Related Art
Trikes have been steadily increasing in popularity in recent times as they provide open air, wind in your face thrills of riding a motorcycle while also offering increased stability and comfort as a result of having three wheels. Because trikes may have a single front wheel, they typically employ steering and suspension systems found in motorcycles.
Motorcycle and bicycle suspensions are used to absorb bumps, cracks, and roadway deformities to provide a rider with a smoother ride and allow the rider to maintain control of the vehicle. A girder fork or girder front end is a common front end suspension in motorcycles and trikes. A traditional girder fork has a pair of uprights that is connected to a front wheel axle on one end and two links on the other end. A spring or springs, most commonly a coil spring(s), connects the lower link to an upper link having a set of handle bars mounted thereon. Leaf springs also have been used in front suspensions. The leaf spring typically is mounted to a bracket extending above the front wheel, and it connects the girder forks or leading or trailing links to the front wheel.
In either case, the girder forks are disposed at an angle, called the steering axis angle or rake, typically between about 20 and 30 degrees short of vertical. As a result, there is an offset between where the wheel touches the ground and where the steering axis intersects the ground, known as a trail. Less rake means less trail, which means a quicker turning bike that is less stable at speed. Conversely, more rake means more trail, which provides a more stable ride at speed but makes the bike more difficult to turn. Rake and trail also lead to a phenomenon known as wheel flop. During wheel flop, the motorcycle turns more than expected due to the front wheel “flopping” over when the handlebars are rotated because the front end of the motorcycle lowers as the handlebars are rotated from side to side.
In both of the aforementioned types of suspensions, steering and suspension are coupled together, meaning when a rider rotates the handle bars to turn the front wheel and ultimately steer the bike, the spring mounted to the girder front end simultaneously moves with all of the components of the girder front end. In addition, the weight of the spring adds to the unsprung weight or weight not supported by the suspension of the bike. Generally, a greater amount of unsprung weight produces a poor ride quality and potential wheel control issues when accelerating or braking. In addition, as the weight of these systems is increased, their coupling to one another makes it difficult to turn for even experienced riders.
The fork front suspension systems used today also suffer a serious disadvantage: the effective wheelbase of the motorbike continually changes. For example, when the motorbike travels over a bump, the front wheel moves up and back relative to the frame, and the wheelbase is shortened, which means less stability at speed.
Another consequence of typical steering and suspension systems is tire wear. Typical motorcycle and trike front wheels are designed to provide braking and turning functionality and are shaped to provide these features. For example, front tires have triangular shapes to assist in turning. Because front tires are not relied upon during acceleration, they also have a thinner tread compared to rear tires. As a result, they tend to wear down easily.
Thus, a need has long existed for even further improved steering and suspension systems and methods for trikes.